Method and system for interrogating an optical fiber sensor of the fiber Bragg grating type, using a tunable optical bandpass filter

A method for interrogating at least one optical fiber sensor of Fiber Bragg Grating (FBG) type, said method comprising:

• lighting said at least one FBG sensor with a broadband excitation optical radiation;
• conveying an optical spectrum transmitted or reflected by the at least one FBG sensor into at least one tunable optical bandpass filter (BPF) comprising a first extraction port and a second transmission port which are complementary to each other;
• tuning the at least one tunable optical bandpass filter BPF at a constant operating wavelength, depending on a nominal operating wavelength of the fiber Bragg grating of the at least one FBG sensor;
• detecting a first optical signal exiting the first extraction port of the at least one tunable optical BPF, said first optical signal being a narrow-band optical filtering of the transmission or reflection spectrum of the fiber Bragg grating of the at least one FBG sensor around the constant operating wavelength of the at least one tunable optical BPF;
• converting, by a first opto-electronic receiver, said first optical signal into a respective first electrical signal, representative of a wavelength shift, with respect to the nominal operating wavelength, of the optical spectrum transmitted or reflected by the fiber Bragg grating of the at least one FBG sensor;
• detecting a second optical signal, exiting the second transmission port of the at least one tunable optical bandpass filter BPF, which is spectrally complementary to the first optical signal;
• converting said second optical signal, by a second opto-electronic receiver, into a respective second electrical signal, representative of a reference optical power which is substantially independent of a filtering wavelength, and having a dependence on power of the broadband excitation optical radiation, and on losses of the overall optical path, equal to the dependence undergone by the first optical signal;
• and
• determining the wavelength shift, with respect to the nominal operating wavelength, of the optical spectrum transmitted or reflected by the fiber Bragg grating of the at least one FBG sensor, based on the first electrical signal detected, deriving from the first optical signal exiting the first extraction port of the at least one tunable optical BPF, and based on the second electrical signal, representative of the reference optical power detected, deriving from the second optical signal exiting the second transmission port of the at least one tunable optical bandpass filter BPF, so that detection of the first electrical signal is compensated for with respect to variations in power of broadband excitation optical radiation and to variations of optical path loss,
• wherein said determined wavelength shift of the optical spectrum transmitted or reflected by the fiber Bragg grating is representative of physical magnitude measured by the at least one FBG sensor;
• and
• wherein said at least one tunable optical BPF, said first opto-electronic receiver and said second opto-electronic receiver are integrated in a photonic integrated circuit (PIC).